As a kind of traction device, interior permanent-magnet synchronous machines (IPMSMs) are widely used in modern electric vehicles. This paper performs a design and comparative study of IPMSMs with different rotor topologies (spoke-type PMs, tangential-type PMs, U-shape PMs, and V-shape PMs). The research results indicate that the IPMSM with V-shape PMs is more satisfying with comprehensive consideration. Furthermore, the IPMSM with V-shape PMs is investigated in detail. The influences of geometrical parameters (magnetic bridge and angle between the two V-shape PMs under each pole, etc.) on the performances of V-shape motor are evaluated based on finite-element method (FEM). For accurate research, the effects of saturation, cross-magnetization, and the change in PM flux linkage on d - and q -axis inductances are considered. The back-electromotive force (EMF), flux leakage coefficient, average torque, torque ripple, cogging torque, power per unit volume, power factor, and flux-weakening ability are investigated, respectively. The experimental results verify the validity and accuracy of the process presented in this paper.

Research on the Performances and Parameters of Interior PMSM Used for Electric Vehicles

Permanent-magnet (PM) motors with both magnets and armature windings on the stator (stator PM motors) have attracted considerable attention due to their simple structure, robust configuration, high power density, easy heat dissipation, and suitability for high-speed operations. However, current PM motors in industrial, residential, and automotive applications are still dominated by interior permanent-magnet motors (IPM) because the claimed advantages of stator PM motors have not been fully investigated and validated. Hence, this paper will perform a comparative study between a stator-PM motor, namely, a flux switching PM motor (FSPM), and an IPM which has been used in the 2004 Prius hybrid electric vehicle (HEV). For a fair comparison, the two motors are designed at the same phase current, current density, and dimensions including the stator outer diameter and stack length. First, the Prius-IPM is investigated by means of finite-element method (FEM). The FEM results are then verified by experimental results to confirm the validity of the methods used in this study. Second, the FSPM design is optimized and investigated based on the same method used for the Prius-IPM. Third, the electromagnetic performance and the material mass of the two motors are compared. It is concluded that FSPM has more sinusoidal back-EMF hence is more suitable for BLAC control. It also offers the advantage of smaller torque ripple and better mechanical integrity for safer and smoother operations. But the FSPM has disadvantages such as low magnet utilization ratio and high cost. It may not be able to compete with IPM in automotive and other applications where cost constraints are tight.

Quantitative Comparison of Flux-Switching Permanent-Magnet Motors With Interior Permanent Magnet Motor for EV, HEV, and PHEV Applications

The torque ripple of a permanent magnet (PM) machine is mainly due to the cogging torque and distortions of the back-emf waveforms, winding inductances and current waveforms. Both the cogging torque and back-emf are normally calculated at open-circuit conditions. However, they are affected by the electric loading and magnetic saturation. This paper investigates the influence of the load conditions on the cogging torque and back-emf waveform by employing a frozen permeability finite element technique. Furthermore, the effectiveness of the rotor skew on the minimization of the cogging torque, thus torque ripple, is also highlighted. It is found that the cogging torque magnitude is significantly increased under load conditions due to more flux leakage through tooth tips. However, the more important issue is that the cogging torque periodicity also changes, thus the rotor skew technique becomes less effective. In addition, the back-emf waveform under load conditions contains more harmonics, which leads to more electromagnetic torque ripple. It is also proven that the cogging torque, back-emf harmonics and consequently the output torque ripple are effectively diminished if the machine is skewed by one actual cogging torque period, i.e., when the electrical loading influence is considered. The analysis results are supported by experimental measurements.

Influence of Electric Loading and Magnetic Saturation on Cogging Torque, Back-EMF and Torque Ripple of PM Machines

In-wheel motors bring a fundamental change in electric vehicle technology by removing conventional mechanical components and freeing up space inside the vehicle body. This approach ultimately helps to realize all-wheel independent control for improved vehicle dynamics and increased vehicle design freedom. However, when space allowed for an in-wheel motor is taken into consideration, high torque density, high efficiency, and wide-speed-range capability are typically required. This paper specifically investigates a 20-pole–24-slot surface permanent magnet synchronous motor with consequent pole rotor for in-wheel direct drive since this topology is well suited for high-pole motors and thus high-torque direct-drive applications. Extensive finite-element analysis is carried out to characterize the proposed motor, and the practical feasibility of the proposed motor is discussed. Finally, the validity of the analysis was experimentally verified.

Development of a 20-Pole–24-Slot SPMSM With Consequent Pole Rotor for In-Wheel Direct Drive

The need for more efficient and renewable means of transport makes the development of hybrid electric vehicles (HEVs) an important topic for both automobile manufacturers and academic researchers. Noise, vibration, and harshness (NVH) of a vehicle are important factors for vehicle users and essential for successful commercialization of this vehicle type. This paper is a compact state-of-the-art review of both NVH characteristics and relevant suppression methods for HEVs. The NVH-related problems are categorized into three categories: engine, powertrain, motor-related. A detailed overview of each category/problem-type is provided, the NVH-suppression methods for different types of HEVs are introduced, and their respective advantages discussed. In addition, emerging developments and ideas for future improvements are summarized. As a result, the paper should be particularly helpful for researchers, who are interested in the development of high-performance HEVs that can provide both substantially improved ride-comfort and reduced energy-consumption.

Noise and vibration suppression in hybrid electric vehicles: State of the art and challenges

Interior permanent magnet synchronous motor (IPMSM) is widely used for many industrial applications such as power train, compressor and home appliances due to its high power density and wide speed range. However, IPMSM have relatively high torque ripple in comparison with surface mounted permanent magnet motor. In case of IPMSM, d-axis current should be fed to use reluctance torque, and the more d-axis current is needed as the motor speed goes up. Therefore, back electromotive force (EMF) of IPMSM contains much harmonics and torque ripple tend to increase as the motor speed increase. This paper proposes a method to reduce torque ripple using harmonic injected current. Firstly dominant harmonic order of back EMF is investigated then under the consideration of harmonics, torque ripple using harmonic injected current will be compared with that of sinusoidal current by finite element analysis.

Torque Ripple Reduction of Interior Permanent Magnet Synchronous Motor Using Harmonic Injected Current

Integrated starter and generator (ISG) is working as starter after vehicle idle stopping and generator during vehicle driving. When ISG works as starter to operate engine, ISG produces maximum power at the operating speed 4000 rpm to remove vibration of initial starting of the engine. In that time ISG produces whine noise which can be detected inside a vehicle. There are two methods to reduce the vibration and noise. One is improving the stiffness of stator and the other is reduction of electromagnetic exciting force. Although improvement of stiffness using mechanical design is utilized effectively to reduce whine noise, the electromagnetic design using the reduction of exciting forces is more reasonable in the same motor size. Because ISG produces torque ripple, radial force and tangential force on operating condition, this paper deals with the reduction design of electromagnetic exciting forces which affect the noise and vibration. Two design variables are selected to optimize the rotor shape especially geometry of flux barrier, and response surface methodology (RSM) is applied as an optimization method. Finally, quantity of the vibration and noise of optimized model are compared with prototype model, and the noise measured in the vehicle engine bay was reduced from 27 dB(A) to 25 dB(A).

Reduction Design of Vibration and Noise in IPMSM Type Integrated Starter and Generator for HEV

This paper presents a design approach to an interior permanent magnetic synchronous motor (IPMSM) for the compressor of a hybrid electric vehicle operated in a 42-V battery system. The approach is to estimate the range of inductance and back-EMF to satisfy the required efficiency of IPMSM. Then, the preliminary geometry satisfying the region is decided by PM type, current density, fill factor, and so on. Last, the detailed design with optimization is performed to consider magnetic saturation and reduce cogging torque and torque ripple. At this time, the simulation results are obtained by finite element analysis and in consideration of operating temperature. In the end, the validity of the design process presented in this paper is verified by test.

Design Process of Interior PM Synchronous Motor for 42-V Electric Air-Conditioner System in Hybrid Electric Vehicle

An improved AC standstill inductance measurement method for interior permanent magnet synchronous machine (IPMSM) is proposed in this paper. Only the 3-phase voltage source, oscilloscope, and DC voltage source are required in this method, rather than the dynamometer and vector controller in the other methods. Depending on the derivative q- and d-axis voltage equations in the stationary reference frame, the q- and d-axis inductances at different current magnetite and vector angle can be calculated by the measured 3-phase voltages and currents. And hence, the saturation and cross-magnetizing effect of the inductances are measurable. This paper will introduce the principle equations, experiment setup, data processing, and results comparison.

Inductance Measurement of Interior Permanent Magnet Synchronous Motor in Stationary Reference Frame

An improved AC standstill inductance measurement method for interior permanent magnet synchronous machine (IPMSM) is proposed in this paper. Only the 3-phase voltage source, oscilloscope, and DC voltage source are required, rather than the dynamometer and inverter in the other methods. Depending on the deduced q- and d-axis voltage equations in the stationary reference frame, the q- and d-axis inductances at different current magnetite and vector angle can be calculated by the measured 3-phase voltages and currents. Thus, the saturation and cross-magnetizing effect of the inductances are measurable. This paper will introduce the principle equations, experiment setup, data processing, and results comparison.

Geun-Ho Lee

Papers

Torque Ripple Reduction of Interior Permanent Magnet Synchronous Motor Using Harmonic Injected Current

Reduction Design of Vibration and Noise in IPMSM Type Integrated Starter and Generator for HEV

Design Process of Interior PM Synchronous Motor for 42-V Electric Air-Conditioner System in Hybrid Electric Vehicle

Inductance Measurement of Interior Permanent Magnet Synchronous Motor in Stationary Reference Frame

An improved AC standstill inductance test method for interior PM synchronous motor considering cross-magnetization effect